To improve the yield of a semiconductor manufacturing apparatus, a defect on the surface of a semiconductor wafer is detected by using a defect inspection device. With the advances in miniaturization in the semiconductor process, even a relatively small defect (having a size that is above several tens of nm) on a semiconductor wafer is required to be managed. This is because even the small defect can adverse the semiconductor process.
As an example of the defect inspection device, there is a dark field optical microscope. The dark field optical microscope detects a defect by irradiating a semiconductor wafer with light and by detecting scattered light from the defect. The dark field optical microscope can detect a defect having a size that is equal to or less than one-tenth of the wavelength of irradiation light.
Factors to determine whether a certain defect can be detected include the wavelength of illumination light, the polarization state of illumination light, the power of illumination light, the size of the spot of illumination light, the scanning method of illumination light, and the irradiation angle of illumination light. The optimum state of some of the factors is different according to the type of a semiconductor wafer and the shape of a defect. In a semiconductor manufacturing factory, an optimum inspection condition is often determined for each type of semiconductor wafer to perform inspection under the one condition.
Patent Literature 1 describes an inspection method by which a specimen is illuminated by alternately switching two illumination lights having different polarization conditions, scattered light from the specimen is detected for each of the illumination lights, and the presence or absence of a defect is determined.